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Ancient bones' DNA draws a direct line to people living today

July 05, 2013|By Eryn Brown
  • Members of the Metlakatla community are working with scientists in genetic studies of Native peoples in British Columbia. Research published this week shows some of them descended directly from ancient inhabitants of the area.
Members of the Metlakatla community are working with scientists in genetic… (Metlakatla Treaty Office )

Anthropologists said this week that DNA from ancient bones from northern British Columbia demonstrates a direct link between long-ago inhabitants and Native American descendants who live in the region today.

Assembling complete mitochondrial DNA genomes from four ancient individuals and three modern ones, the team found that living people had the exact same sequences found in bones that were thousands of years old — proving “definitively,” they said, that the native communities had been in the region a very, very, very long time.

“We’re showing there’s a long-term affinity with the present-day First Nations population, going back 5,000 years,” said Jerome Cybulski, former curator of physical anthropology at the Canadian Museum of Civilization in Gatineau, Quebec, and coauthor of a paper describing the research that was published Wednesday in the journal PLOS ONE.

To reveal the genetic ties, anthropologist Ripan Malhi of the University of Illinois at Urbana-Champaign and colleagues looked at mitochondrial DNA, which helps direct how the cellular powerhouses called mitochondria generate energy in the body.  Mitochondrial DNA, unlike the so-called nuclear DNA that carries every organism’s genetic blueprint, is passed down directly from mothers to offspring, without any mixing with DNA from the father. 

Geneticists have used mitochondrial DNA to probe ancient bloodlines for decades, usually concentrating on a small segment of the DNA called HVS1 to determine whether individuals are related.  For this study, Malhi and his colleagues also started off by concentrating on such short segments, in both ancient and modern mitochondrial DNA samples.  Finding striking similarities between a few of the ancient and living people in those short sequences, they then went on to sequence the entire mitochondrial genomes — 16,500 DNA letter pairs apiece — of the individuals.  

They found that the most ancient bones, at around 6,000 years old, shared a genetic lineage with another, previously studied ancient person who was 2,500 years old, and who could be linked to a living person.  The three living people Malhi’s team sequenced were all shown to share their genetic lineage with an individual who lived more than 5,000 years ago.

Such ties might be reflected in the oral histories of the native people, Malhi said.  For instance, some oral histories describe ancient relationships between internal groups in the regions, involving tales of movement and intermarriage between communities.  Malhi said such relationships might be apparent in the ancient and modern genetic record.

Being able to look at the entire mitochondrial genome — and not just a short portion of it — added confidence that the connections are real, he said.

“We’re finding links back to 5,000 years for mitogenomes that are fairly specific to the region,” Malhi said.  “If you only looked at HVS1, we could have been able to possibly think there was a connection, but it would have been less definitive.”

“We can now understand better the relationship of ancient lineages to modern lineages,” said Jennifer Raff, an anthropological geneticist at Northwestern University in Evanston, Ill. who was not involved in the research. “We want to know how populations relate to each other.”

Raff said she would like to see entire mitochondrial genomes sequenced for more ancient individuals. Malhi said he planned in the future to study Y chromosomes from ancient and living men (which record lineages passed directly from father to son) and exomes, or the DNA that codes for genes, to explore how Native American genomes evolved as colonizing Europeans carried infectious diseases into the continent.

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